1. Technical Field
The present invention relates in general to an improved wear bushing, and in particular to an improved bit run and retrieval wear bushing and tool.
2. Description of the Prior Art
A wear bushing is used in drilling applications to protect the inner profiles of the various components in the wellhead. In the prior art, wear bushings typically have been run or lowered down to the wellhead on a separate trip. One type of bit run wear bushing is held to a tool via shear pins. This bit run wear bushing has an internal ledge with a reduced inner diameter for retrieval. However, the tools used to run and retrieve the wear bushings occasionally release the wear bushings prematurely, and do not have full opening through the wear bushing. Thus, an improved bit run wear bushing would be desirable.
A wear bushing has a lower portion that is landed on a casing hanger in a wellhead housing. The upper end of the lower portion of the wear bushing has a shear ring in a locking profile that locks the wear bushing to the casing hanger. A locking ring resides in a bore of the wear bushing and has passages for fluid flow. The inner surface of the locking ring has teeth for engaging the teeth of a running tool when the tool is moved upward relative to the wear bushing. The ring is designed so that the only profile moving up or down in the drill string that will engage the ring is the profile on the tool. A plurality of locking keys extend radially inward through the bore of the wear bushing beneath the locking ring. The keys are designed to allow free rotation of the tool relative to the wear bushing in only one direction. A beveled ridge on the tool mates with the locking ring.
The wear bushing is mounted to the tool which is joined to a drill string. With the locking keys locked on the tool, the wear bushing is lowered down the well into the wellhead housing. The wear bushing is landed on the casing hanger and the locking pins are pressed upward as they contact a seal assembly. The wear bushing is rotated until the locking pins align and fall into slots. With the locking pins in the slots, the wear bushing cannot be rotated relative to the casing hanger. The tool is released from the wear bushing by more rotation and a downward force on the tool that will expand the C-ring and release the tool, and the tool may then be run deeper into the well.
The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the preferred embodiment of the present invention, taken in conjunction with the appended claims and the accompanying drawings.